Investigation of the Direction of Spontaneous Magnetisation at 0 K in HoCo2 and TmFe2

The direction of spontaneous magnetisation at 0 K across a phase orientation boundary in rare-earth laves phase compounds is computed as a function of the ratio of magnetic to electrostatic interactions. The phase boundary and range of parameters used for the computation correspond to the portion of the orientational phase diagram where experimental data can be obtained. In the series of pseudo-binary compounds (Gdx Ho1-x )Co2 and (Yx Ho1-x )Co2 the range of parameters covers the continuous transition from the 100 to the 110 orientations. The nmr measurements on this series show that the direction of spontaneous magnetisation is at intermediate orientation between the 100 and 110 directions. The material TmFe2, which is in the vicinity of a discontinuous orientational boundary, is also discussed.